756457721 has 8 divisors (see below), whose sum is σ = 828574920. Its totient is φ = 687409408.

The previous prime is 756457717. The next prime is 756457733. The reversal of 756457721 is 127754657.

756457721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 147355321 + 609102400 = 12139^2 + 24680^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 756457721 - 2² = 756457717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (756456721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 766706 + ... + 767691.

It is an arithmetic number, because the mean of its divisors is an integer number (103571865).

Almost surely, 2^756457721 is an apocalyptic number.

It is an amenable number.

756457721 is a deficient number, since it is larger than the sum of its proper divisors (72117199).

756457721 is a wasteful number, since it uses less digits than its factorization.

756457721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1534443.

The product of its digits is 411600, while the sum is 44.

The square root of 756457721 is about 27503.7764861482. The cubic root of 756457721 is about 911.1605050716.

The spelling of 756457721 in words is "seven hundred fifty-six million, four hundred fifty-seven thousand, seven hundred twenty-one".